Faculty

Savaldi-Goldstein Sigal , Associate Professor

Research Interests

One
of the most striking features of multicellular organisms is their ability to
coordinate information from the various cell types and tissues comprising a
single functional organ unit. Unlike animals, plants produce new organs and adjust
their growth throughout their life span. In addition, plant cells are held
together by a rigid cell wall and do not migrate. These inherently distinct
features demand specialized control mechanisms of the growing tissues, to
ensure appropriate organ size and shape. How do different cells manage to grow in
synchrony and modulate their growth in response to a changing environment?

Small molecule hormone signalling pathways lie at the heart
of this growth control.Despite dramatic
advances in identifying signalling components, understanding of their
spatiotemporal activities and how they integrate to coordinate whole-organ
growth is just beginning to take form.Our research focuses on the steroid hormone brassinosteroid (BR)
signalling pathway. The BR activity triggers growth of above and below-ground
organs, but also inhibits growth.We are
currently seeking to understand how the different cell types decode the BR
signal and how this information is interpreted at the organ level.

Using the
Arabidopsis thaliana root as a model organ, our studies have demonstrated
that the spatial distribution of BR activity is an important fine-tuning
determinant of root growth. In certain cell types, BR signaling drives cell
elongation and cell proliferation (See Hacham et al., 2011, Development), while in others, it restrains them (See
Fridman et al., 2014, Genes and Dev. andVragović, Sela et al., 2015,
PNAS). To uncover the molecular genetic framework underlying the
differential developmental programs triggered by BR, we established a precise,
high-resolution polyribosome-associated mRNA map of temporal and
tissue-specific BR responses in various mutant backgrounds. The opposing effect
of the hormone on gene expression in the outer epidermal tissue versus the
innermost tissues was clearly demonstrated (Vragović, Sela et al., 2015,
PNAS). We revealed that BR activity in the inner tissues buffers the
promoting effect of the hormone in the epidermis, thus providing a balanced
growth.

In
parallel, we investigate whether BR-mediated root growth is modulated by
environmental signals. We have found that activity of key downstream BR
transcription factors blocks root developmental reprogramming in response to
low phosphate availability (See Singh et al., 2014, Plant Physiology). Since soluble phosphate levels in many soils are suboptimal for plant growth and productivity, our findings present new research avenues toward understanding how developmental reprogramming is achieved and potential biotechnological means of improving plant performance.